Ideas

breadcrumb based on a navigation which genarated by wp_nav_menu()

formlessMember

Since wp_nav_menu() can mix almost anything (page, cat, link...) in a branch of site-tree after WP3.0, the breadcrumb-generating plugins which already exist cannot handle the non-wp_list_pages() all-mixed-up site-tree as far as I know.
For WP, wp_nav_menu() is a big step ahead as CMS, but at once needs genuine breadcrumb system which go perfect with wp_nav_menu(), I think.